In recent years, with the advancements in semiconductor devices to be tested, there is an increasing demand for improvements in the performance of semiconductor test systems. Specifically, there is a need for test systems that can operate at frequencies in the RF band range (i.e., RF test signals) and perform even higher precision testing.
Conventional semi-conductor test systems generally include a test head which provides an interface between a mainframe of a testing equipment and a device under test (DUT), as well as a prober which makes positioning of the DUT. Usually, within the test head, a DUT board having a plurality of conductive pads is mounted onto the connecting surface to the prober for the electrical connection to the mainframe of the testing equipment. On the other hand, on the upper surface of the prober (the connecting surface to the test head) is mounted a connection ring through which a plurality of pogo pins pierce. A probe card having contact needles for probing the DUT is mounted on the prober side of the connection ring. The probe card is also equipped with a plurality of electrically conductive pads through which the probe card is electrically connected to the pogo pins of the connection ring.
The wafer on which the DUT is fabricated is normally located on the top of a prober chuck (wafer table). On testing, the test head and the prober are docked together, during which the pogo pins of the connection ring are compressed onto the electrically conductive pads which are arranged at predetermined places on the DUT board. In addition, the operation of the prober chuck causes the wafer to move to a position where the contact needle of the probe card makes contact with the DUT on the wafer. In this way, the test device and the DUT are electrically connected. That is to say, a reliable electrical connection can be made by using the method of pressing pogo pins against conductive pads, without utilizing a connector which has a latching mechanism such as engagement by snapping in or a screw like the SMB connector, the SMA connector or the like. The above arrangement has been indispensable in performing tests in which connection and disconnection between the test head and the prober are repeated automatically and successively.
When performing tests with DC signals and low frequency signals in a semi-conductor testing system, the testing accuracy can be maintained even with the above connection method. However, when handling RF band signals, the use of the pogo pins causes a reduction of frequency-response characteristic due to reflection loss and so forth. Accordingly, when handling RF band signals, an RF coaxial connector must be used for such connection. As is shown in FIG. 4 of the present application, RF coaxial connectors are assembled directly onto the probe card, and the operator must manually connect the connectors and the RF coaxial connectors on the test head side one by one. With this approach, a full automatic connection of the test head and the prober is impossible to accomplish, and intervention by the operator is required at the time of connection and disconnection. This causes a significant decrease in the test throughput.
Furthermore, the conventional connector is directly assembled to the conventional probe card, as shown in FIG. 4. Even when only one of the connectors breaks or becomes defective, replacement of the entire probe card or replacement of the broken connector is necessary. The replacement of the entire probe card is cost prohibitive; and the replacement of a broken connector is difficult because the connector is directly assembled to the probe card.
As shown in FIG. 6, in order to dock the test head with the prober, a hinge mechanism 603 is employed to link a test head 601 to a prober 602. However, automatic connection by way of a coaxial connector for RF band signals may not work properly. That is to say, at the moment the connector of the test head side is coupled to the connector of the prober side, if the connection surfaces are not parallel, then the central axes of the connectors of both sides are not aligned, resulting that these connectors may not connect smoothly.
One approach to remedy the above connection problem is through the use of a floating mount apparatus for the coaxial connector that is disclosed in a co-pending U.S. patent application Ser. No. 08/932,762 by the applicants entitled "Floating Mount Apparatus For Coaxial Connector," which is assigned to the same assignee as the present invention and incorporated herein by reference. FIG. 5 illustrates a cross-section of such a floating mount apparatus. That is, the central axis of the connector on the prober side tilts on connection with the central axis of test head by way of the free movement in any direction of the connector on the prober side, allowing appropriate tilt of the central axis.
However, when the floating mount apparatus of the coaxial connector is directly mounted onto the probe card, a protrusion in the form of a flange nut 506 (FIG. 5) extends outwards from the wafer side of the probe card and, thus, interferes with the wafer. It is also difficult to maintain coaxial structure in the connection to a pattern of the connectors on the probe card from the connectors on the test head side. Therefore, it is necessary to develop a new arrangement which can have the floating mechanism mounted onto the probe card without interfering with the wafer and can maintain a coaxial structure even in the connecting section to the trace on the probe card.
Another problem with such test systems is associated with the variation of the stroke of the probe chuck lifting depending on the models of probers. When a connection ring suited for one model of probers is used with some other model, even if the probe chuck of the other model is raised to its maximum height, the DUT still may not be able to reach the probe card. In this case, a new connection ring that matches the chuck lifting stroke of the other model of probers must be designed and manufactured. This causes the production cost of the connection ring to increase.
Accordingly, it is an object of the present invention to remedy the problems of the aforementioned prior art in the probe card.
It is a further object of the invention to provide an improved probe card with an RF coaxial connector which can be used to perform full automatic connection with the connector of the test head.
Another object of the invention is to provide a probe card apparatus that has the ability to improve the throughput of the test system.